After black forest, you go to swamp, but you will likely encounter mountains before then as every black forest has a mountain at the center (at least in my experience), that being said don't go there until you have visited the swamps. As for now progression goes meadows/black forest/swamp/mountains/plains. There are other boimes but they are empty until more content is added. You might not find all biomes on your starter island so sailing is key to discovering new areas.